This invention relates to molded plastic containers and closures and more particularly to a closure having a tear-band which, when torn away, makes the closure easier to remove from the container.
It is known to provide plastic shipping containers and closures with secure locking arrangements which require some type of physical alteration to the closure structure before it can be easily removed from the container. For example, some closures are provided with small apertures in the peripheral skirt to permit the skirt to be split or fractured at several circumferentially spaced locations. The loss of integrity in the skirt allows sections of it to be pulled outwardly such that they pass more readily over a locking flange formed on the top of the container when one wishes to remove the closure from the container.
Another example of a closure requiring physical alteration for removal is the tear-band closure. The skirt portion of this type of closure is provided with a circumferential tear line of structural weakness which allows a lower portion of the skirt to be torn away thus to eliminate some or all of a locking arrangement between the container and closure.
Both the fracturable skirt closure and the tear-band closure have the characteristics of providing a strong lock when first applied, providing evidence of tampering, and providing a measure of resealability even after the locking structure has been altered or removed.
This invention is described with reference to a molded plastic container/closure combination of the type having a tear-band in the closure skirt for removability. The invention provides a strong pre-tear lock and seal, a strong post-tear seal and improved post-tear removability.
In general, the invention is applied to a plastic container having an outwardly formed top rim and first and second ring-like outwardly-extending flanges formed on the container sidewall at first and second locations below the top rim. The closure is of the type having an inverted U-shaped peripheral channel which receives the container rim therein and seals thereto when fully set in place. The outermost interior wall of the closure channel is provided with first and second circumferentially continuous, inwardly extending protrusions, the top-most of which coacts with the container rim to provide a first lock and the lower-most of which coacts with the top ring-like flange on the container outer sidewall to provide a second lock. The lower sidewall flange is closely adjacent the bottom of the closure skirt to make it difficult or impossible to pull outwardly on the skirt.
A tear line; i.e., a line of structural weakness which is more easily torn or fractured than the balance of the closure skirt, is formed in the skirt between the upper and lower protrusions such that physical removal of the tear-band eliminates the second lock thereby facilitating removal of the closure from the container.
In the preferred embodiment disclosed herein, the tear line is irregular or zig-zag in design thereby to create a plurality of circumferentially spaced tabs or grasp areas which extend toward but are spaced from the topmost of the flanges. The topmost flange is preferably made discontinuous or segmented as to provide spaced areas of maximum clearance between the grasp tabs and the bottom-most side flange. The closure and lid are designed so that such areas of maximum clearance are guaranteed to occur no matter what the angular relationship between the closure and the container when the closure is applied.
Also in the preferred embodiment, the inner wall of the closure is made deeper than normal and fits against a step in the inner container wall to stabilize the closure under heavy loading conditions such as occur when filled containers are stacked.
Other arrangements for applying the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.